Method for detaching layers with low magnetic permeability

ABSTRACT

A method for detaching a first material layer from a second material layer includes following steps: forming a high-magnetic-permeability material layer on a first material layer comprised of low-magnetic-permeability material; removing a portion of the high-magnetic-permeability material layer to expose a portion of the first material layer; epitaxially growing a second material layer comprised of low-magnetic-permeability material on the exposed portion of the first material layer and the high-magnetic-permeability material layer; cooling the first and second material layers; heating the high-magnetic-permeability material layer, thus detaching the first material layer from the second material layer.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional application of patentapplication Ser. No. 12/693,503, filed on Jan. 26, 2010, entitled“METHOD FOR DETACHING LAYERS WITH LOW MAGNETIC PERMEABILITY”, assignedto the same assignee, which is based on and claims priority from ChinesePatent Application No. 200910305742.4, filed in China on Aug. 18, 2009,and disclosure of which is incorporated herein by reference in itsentirety.

BACKGROUND

1. Field of the Invention

The present disclosure relates generally to a method for detachingmaterial layers, and more particularly, to a method for detachingmaterial layers of a semiconductor device.

2. Description of Related Art

A building block of many electronic devices such as diodes, transistors,and lasers is usually made of semiconductor material that can be grownover a substrate. The semiconductor material is fabricated by growing anepitaxial layer of the semiconductor material upon a substrate. Forexample, a light emitting diode (hereafter LED) is fabricated by growingan epitaxial layer of III-Nitride semiconductor on a sapphire substrateusing a method of metal-organic chemical vapor deposition.

However, the sapphire substrate has a weak thermal conductivity, suchthat heat can not be dissipated efficiently out of the LED. This willreduce the light emitting efficiency of the LED. On the other hand, thesapphire substrate has a lattice parameter different from theIII-Nitride semiconductor, thereby having a different expansioncoefficient from the III-Nitride semiconductor. The difference ofexpansion coefficients may result in distortion of the sapphiresubstrate or the III-Nitride semiconductor when a temperature of the LEDis high. Thus, the sapphire substrate is required to bedetached/separated from the LED after growing epitaxial layer ofIII-Nitride semiconductor.

Typically, the sapphire substrate is detached from the LED by applying amethod of laser lift off melt the epitaxial layer at its interface withthe substrate on which is grown. However, the laser has high energy,which is absorbed by the epitaxial layer. This may break a latticestructure of the epitaxial layer, thereby resulting in quality reductionof the LED.

Therefore, there is a need in the art for method for detaching layers,which overcomes the above-mentioned problems.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present embodiments.Moreover, in the drawings, all the views are schematic, and likereference numerals designate corresponding parts throughout the severalviews.

FIG. 1 is a flow chart of a method for detaching a material layer from amultilayer structure in accordance with a first exemplary embodiment.

FIG. 2A-FIG. 2E are cross-sectional views illustrating successive stagesof the method for detaching a layer from a multilayer structureaccording to an alterative embodiment

FIG. 3A-FIG. 3B are cross-sectional views illustrating temperaturegradients of the multilayer structure of FIG. 2( c) without and with acooling substance applied.

FIG. 4 is a flow chart of a method for detaching a material layer from amultilayer structure in accordance with a second exemplary embodiment.

FIG. 5A-FIG. 5F are cross-sectional views illustrating successive stagesof the method for detaching a material layer from a multilayer structureas shown in FIG. 4.

FIGS. 6A and 6B are cross-sectional views illustrating successive stagesof a method for detaching a material layer from a multilayer structurein accordance with a third exemplary embodiment.

FIG. 7A-FIG.7C are cross-sectional views illustrating successive stagesof a method for detaching a material layer from a multilayer structurein accordance with a fourth exemplary embodiment.

FIGS. 8A and 8B cross-sectional views illustrating successive stages ofa method for detaching a material layer from a multilayer structure inaccordance with a fifth exemplary embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, a method for detaching a material layer from amultilayer in accordance with a first exemplary embodiment is provided.In this embodiment, the method is used for detaching one semiconductorlayer from another semiconductor layer, or one semiconductor layer froman insulating layer. Referring to FIG. 2, the method is described indetail as follows.

Step 12: a high-magnetic-permeability material layer is formed on afirst material layer.

Referring to FIG. 2A, a high-magnetic-permeability material layer 104 isformed on a surface of a first material layer 102 by sputtering or vaporplating. The first material layer 102 is made of alow-magnetic-permeability material. In this embodiment, the firstmaterial layer 102 can be a semiconductor material or an insulatingmaterial.

The high-magnetic-permeability material layer 104 can be selected fromthe group consisting of molybdenum-metal (Mo-metal), permalloy,electrical steel, Nickel zinc ferrite, manganese zinc ferrite, steel andnickel. Generally, a magnetic permeability of thehigh-magnetic-permeability material layer 104 is at least 10² timeslarger than that of the first material layer 102. For example, when thefirst material layer 102 is sapphire having a magnetic permeability of1.25 N/A², the corresponding high-magnetic-permeability material layer104 may have a magnetic permeability of equal to or more than 125 N/A².A table showing magnetic permeability values of somehigh-magnetic-permeability materials and the sapphire is illustratedbelow.

Coefficient of Magnetic material magnetization (×10⁻⁶N/A^(e)) Magneticfield Mo-metal 20,000 25000 at 0.002 T permalloy 8000 10000 at 0.002 Telectrical steel 4000 5000 at 0.002 T (ρ = 0.011 μΩ · m) nickel zincferrite 20-800 manganese zinc >800 ferrite steel 700 875 at 0.002 Tnickel 100 125 at 0.002 T sapphire −2.1 × 10⁻⁷ 1.2566368

Step 14: a second material layer is formed on thehigh-magnetic-permeability material layer.

Referring to FIG. 2B, a second material layer 106 is formed on thehigh-magnetic-permeability material layer 104. The second material layer106 is made of a low-magnetic-permeability material. The first materiallayer 102, the high-magnetic-permeability material layer 104 and thesecond material layer 106 cooperatively form a multilayer structure 100.Generally, a magnetic permeability of the high-magnetic-permeabilitymaterial layer 104 is at least 10² times larger than that of the secondmaterial layer 106. In this embodiment, the second material layer 106can be a semiconductor material or an insulating material. In analternative embodiment, the second material layer 106 can be the same tothe first material layer 102, such that the first and second materiallayers 102 and 106 are gallium nitride. In another alternativeembodiment, the second material layer 106 can be different from thefirst material layer 102, such that the first material layer 102 issapphire and the second material layer 106 is gallium nitride.

Step 16: the first and second material layers are cooled and thehigh-magnetic-permeability material layer is heated by applying a radiofrequency electromagnetic wave having a high radio frequency thereto.Thus, the first and second material layers shrink and thehigh-magnetic-permeability material layer expands, such that a stressforce is generated between the first material layer and thehigh-magnetic-permeability material layer and between the secondmaterial layer and the high-magnetic-permeability material layer. Thefirst material layer or the second material layer is detached from thehigh-magnetic-permeability material layer. That is, the first and secondmaterial layers are detached from each other.

Referring to FIG. 2C, the first material layer 102 and the secondmaterial layer 106 are cooled by applying a cooling substance 108. In analternative embodiment, the cooling substance 108 can be cooling fluid,such as liquid nitrogen, dry ice, low temperature air, low temperaturewater and etc. A cooling process for the first and second materiallayers 102 and 106 is described in detail as follows. The multilayer 100is placed in a vacuum cavity (not shown). Then the cooling substance 108is introduced into the vacuum cavity to cool the first and secondmaterial layers 102 and 106. Meanwhile, the high-magnetic-permeabilitymaterial layer 104 is also cooled. In an alternatively embodiment, thefirst and second material layers 102 and 106 can also be cooled byapplying a cooling device, such as one or more thermoelectric coolers.At this moment, the first material layer 102 contacts a cold end of athermoelectric cooler, and the second material layer 106 contacts a coldend of another thermoelectric cooler.

A high-frequency radiofrequency electromagnetic wave 110 is provided.Then the multilayer structure 100 is placed in the high-frequencyradiofrequency electromagnetic wave 110. A frequency of thehigh-frequency radiofrequency electromagnetic wave 110 is in a rangefrom 3 gigahertz (GHz) to 300 GHz. It is well known that a highmagnetic-permeability material 104 in a high-frequency radiofrequencyradio field will generate a high temperature by absorbing thehigh-frequency radiofrequency electromagnetic wave 110. In analternative embodiment, the high-frequency radiofrequencyelectromagnetic wave 110 can be generated by a wire winding, which isarranged around the multilayer 100. At this moment, temperatures of thefirst and second material layers 102 and 106 almost remain unchanged forthe magnetic-permeability thereof is low.

In this case, the high-magnetic-permeability material layer 104 expandsaccording to increase in temperature, and the first and second materiallayers 102 and 106 shrink according to cooling by the cooling substance108. A first stress force is generated between the first material layer102 and the high-magnetic-permeability material layer 104, and a secondstress force is generated between the second material layer 106 and thehigh-magnetic-permeability material layer 104. As the temperature of thehigh-magnetic-permeability material layer 104 increases gradually, thestress force increases correspondingly. Referring to FIG. 2D, when thetemperature of the high-magnetic-permeability material layer 104 reachesa certain value, the first stress force becomes larger than a bondingforce between the first material layer 102 and thehigh-magnetic-permeability material layer 104. At this moment, the firstmaterial layer 102 is detached from the high-magnetic-permeabilitymaterial layer 104. Alternatively, referring to FIG. 2E, when thetemperature of the high-magnetic-permeability material layer 104 reachesa certain value, the second stress force becomes larger than a bondingforce between the second material layer 106 and thehigh-magnetic-permeability material layer 104. Thus the first and secondmaterial layers 102 and 106 are detached from each other.

After the first and second material layers 102 and 106 are detached fromeach other, a cleaning step is provided. The cleaning step includingremoving the high-magnetic-permeability material on the first and secondmaterial layers 102 and 106 by chemical mechanical polishing, chemicalwet etching or dry etching.

FIG. 3A-FIG. 3B illustrate temperature gradients of the multilayerstructure 100 in FIG. 2C with and without the cooling substance 108applied. In this embodiment, the temperature gradients distribute alonga direction perpendicular to the first material layer 102, the secondmaterial layer 106 and the high-magnetic-permeability material layer104. As shown in FIG. 3A, a temperature gradient of the multilayerstructure 100 without the cooling substance 108 applied is shown at theright hand of the multilayer structure 100. As shown in FIG. 3B, atemperature gradient of the multilayer structure 100 with the coolingsubstance 108 applied is shown at the right hand of the multilayerstructure 100. From the two temperature gradients as shown in FIGS. 3Aand FIG. 3B, it is seen that the temperature of the multilayer structure100 decreases gradually from a middle of the high-magnetic-permeabilitymaterial layer 104 to the first and second material layers 102 and 106respectively. The difference between FIGS. 3A and 3B is that, thetemperature gradient in FIG. 3A shows two straight lines and the FIG. 3Bshows two arc lines. That is, difference in temperature between thehigh-magnetic-permeability material layer 104 and the first and secondmaterial layer 102 and 106 with the cooling substance 108 is larger thanthat without the cooling substance 108. Thus, the stress force betweenthe high-magnetic-permeability material layer 104 and the first andsecond material layer 102 and 106 with the cooling substance 108 islarger than that without the cooling substance 108.

Referring to FIG. 4, a method for detaching a material layer from amultilayer of a second exemplary embodiment is provided. In thisembodiment, the method is used for detaching one semiconductor layerfrom another semiconductor layer, or one semiconductor layer from aninsulating layer. Referring to FIG. 5A-FIG. 5F, the method is describedin detail as follows.

Step 22: a high-permeability material layer is formed on a firstmaterial layer.

Referring to FIG. 5A, a high-permeability material layer 204 is formedon a surface of a first material layer 202 by sputtering or vaporplating. The first material layer 202 is a low-magnetic-permeabilitymaterial. In an alternative embodiment, the first material layer 202 canbe a semiconductor material, such as an element semiconductor or acompound semiconductor. The element semiconductor can be silicon orgermanium. The compound semiconductor can be selected from the groupconsisting of IV-IV semiconductor, III-V semiconductor, and II-VIsemiconductor. The III-V semiconductor is one of a material for formingan LED. The III-V semiconductor material can be selected from the groupconsisting of an AlGaInP-based material, an AlGaInN-based material, andan AlGaAs-based material. The AlGaInN-based material can be selectedfrom the group consisting of AlN, GaN, InN, AlGaN, GalnN, AlInN, andAlGaInN. In this alternative embodiment, the first material layer 202can be formed by liquid-phase epitaxy (LPE), vapor-phase epitaxy (VPE),metal organic chemical vapor deposition, (MOCVD) and molecular beamepitaxy (MBE). In another alternative embodiment, the first materiallayer 202 can also be an insulating material, such as sapphire. Thehigh-magnetic-permeability material layer 204 has a same material to thehigh-magnetic-permeability material layer 104 of the first exemplaryembodiment.

Step 24: a portion of the high-magnetic-permeability material layer isremoved to expose a portion of the first material layer.

Referring to FIG. 5B, a portion of the high-magnetic-permeabilitymaterial layer 204 is removed by applying a photolithography method,such that a portion of the first material layer 202 is exposed. In theillustrated embodiment, the exposed portion of the first material layer202 forms a patterned structure as lattice structure. A reason forexposing the first material layer 202 is that thehigh-magnetic-permeability material layer 204 is a material not capableof epitaxial growth of a second material layer 206 in a latter step 26.Thus the second material layer 206 can be epitaxially grown on theexposed first material layer 202.

Step 26: a second material layer is epitaxially grown on the exposedportion of the first material layer, and covers thehigh-magnetic-permeability material layer.

Referring to FIGS. 5C and 5D, the second material layer 206 isepitaxially grown on the exposed portion of the first material layer 202and covers the entire surface of the high-magnetic-permeability materiallayer 204. The second material layer 206 can be a semiconductor materialor an insulating material. A material of the second material layer 206can be same to the first material layer 202, for example they both areGaN. The material of the second material layer 206 can also be differentfrom that of the first material layer 202, for example the firstmaterial layer 202 is sapphire and the second material layer is GaN.

Step 28: the first and second material layers are cooled and thehigh-magnetic-permeability material layer is heated by applying a radiofrequency electromagnetic wave having a high radio frequency thereto.Thus the first and second material layers shrink and thehigh-magnetic-permeability material layer expands, such that a stressforce is generated between the first material layer and thehigh-magnetic-permeability material layer and between the secondmaterial layer and the high-magnetic-permeability material layer. Thefirst material layer or the second material layer is detached from thehigh-magnetic-permeability material layer. That is, the first and secondmaterial layers are detached from each other.

Referring to FIGS. 5E and 5F, a cooling method for the first and secondmaterial layers 202 and 206 is similar to the cooling method asdescribed in the first exemplary embodiment, and the heating method forthe high-magnetic-permeability material layer 204 by applyinghigh-frequency radiofrequency electromagnetic wave 108 is similar to theheating method of the first exemplary embodiment. For the same reason tothe first exemplary embodiment, the first material layer 202 or thesecond material layer 206 is detached from thehigh-magnetic-permeability material layer 204. As shown in FIG. 5F, inthis embodiment, the first material layer 202 is detached form thehigh-magnetic-permeability material layer 204.

After the first and second material layers 202 and 206 are detached fromeach other, a cleaning step is provided. The cleaning step includingremoving the high-magnetic-permeability material on the first and secondmaterial layers 202 and 206 by chemical mechanical polishing, chemicalwet etching or dry etching.

Referring to FIGS. 6A and 6B, a method for detaching two layers of amultilayer structure in accordance with a third exemplary embodiment isprovided. The method is similar to the method of second exemplaryembodiment. The method of this embodiment differs from the method ofsecond exemplary embodiment is described as follows. A multilayer 300 ofthis embodiment includes three semiconductor layers 302, 306 and 310stacked one after another in the above order. A firsthigh-magnetic-permeability material layer 304 is arranged between thesemiconductor layers 302 and 306, and a secondhigh-magnetic-permeability material layer 308 is arranged between thesemiconductor layers 306 and 310. The first and secondhigh-magnetic-permeability material layers 304 and 308 each have apatterned structure to exposed semiconductors 302 and 306, such that thesemiconductor layer 306 epitaxially grown on an exposed portion of thesemiconductor layer 302 and the semiconductor layer 310 epitaxiallygrown on a exposed portion of the semiconductor layer 306. Similar tothe second exemplary embodiment, the semiconductor layers 302, 306 and310 are cooled by the cooling substance 108, and thehigh-magnetic-permeability material layers 304 and 310 are heated by thehigh-frequency radiofrequency electromagnetic wave 110, such that thesemiconductor layers 302, 306 and 310 are detached from each other.

After the semiconductor layers 302, 306 and 310 are detached from eachother, a cleaning step is provided. The cleaning step including removingthe high-magnetic-permeability materials on the semiconductor layers302, 306 and 310 by chemical mechanical polishing, chemical wet etchingor dry etching.

Referring to FIG. 7A-FIG. 7C, a method for detaching a layer from amultilayer structure in accordance with a fourth exemplary embodiment isprovided. In this embodiment, the method is used for detaching twolayers with a same material. This method is similar to the method of thesecond exemplary embodiment. A multilayer structure of this embodimentis an LED 40. This method is used for detaching a sapphire substrate 42from the LED 40. The LED 40 includes the sapphire substrate 42, a GaNbuffer layer 44, a functional structure 46 and a metal substrate 48stacked one after another in the above order. The functional structure46 includes an N-type GaN layer 462, a multi-quantum well layer 464 anda P-type GaN layer 466. A high-magnetic-permeability material layer 442is formed in the GaN buffer layer 44. The high-magnetic-permeabilitymaterial layer 442 includes a patterned structure, such that the GaNbuffer layer 44 includes two layers partly partitioned by thehigh-magnetic-permeability material layer 442 and forming a single body.

The cooling method for the GaN buffer layer 44 is similar to the coolingmethod as described in the first exemplary embodiment, and the heatingmethod for the high-magnetic-permeability material layer 442 by applyinghigh-frequency radiofrequency electromagnetic wave 108 is similar to theheating method of the first exemplary embodiment. For the same reason tothe first exemplary embodiment, the two layers of the GaN buffer layer44 are detached from each other. That is, the sapphire substrate 42 isdetached from the LED 40.

Referring to FIGS. 8A and 8B, a method for detaching a layer from amultilayer structure in accordance with a fifth exemplary embodiment isprovided. In this embodiment, materials of the two detached layers aredifferent. In the illustrated embodiment, the method is used fordetaching a sapphire substrate 52 from an LED 50. The LED 50 is similarto the LED 40 of the fourth embodiment and the difference is that ahigh-magnetic-permeability material layer 542 is arranged between thesubstrate 52 and a GaN buffer layer 54. Similar to the method of thefourth exemplary embodiment, a cooling method for the GaN buffer layer54 and the sapphire substrate 52 and a heating method for thehigh-magnetic-permeability material layer 542 are applied, such that thesapphire substrate 52 is detached form the LED 50.

The above methods for detaching a layer from a multilayer structureapply a cooling substance to cool the low-magnetic-permeability materiallayers and apply a high-frequency radio frequency electromagnetic waveto heat the high-magnetic-permeability material layer sandwiched betweenthe low-magnetic-permeability material layers, and thus thelow-magnetic-permeability material layers are detached from each otherbecause of the stress force. This can prevent from breaking the latticestructure of the low-magnetic-permeability material layers.

It can be understood that the above-described embodiment are intended toillustrate rather than limit the disclosure. Variations may be made tothe embodiments and methods without departing from the spirit of thedisclosure. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the scope of thedisclosure.

1. A method for detaching a first material layer from a second material layer, comprising: forming a high-magnetic-permeability material layer on the first material layer; removing a portion of the high-magnetic-permeability material layer to expose a portion of the first material layer; epitaxially growing the second material layer on the exposed portion of the first material layer, the second material layer covering the high-magnetic-permeability material layer, wherein the first and second material layers are comprised of low-magnetic-permeability materials; cooling the first and second material layers such that the first and second material layers shrink; and heating the high-magnetic-permeability material layer using a high-frequency radiofrequency electromagnetic wave such that the high-magnetic-permeability material layer expands, thus detaching the first material layer from the second material layer.
 2. The method of claim 1, wherein a material of each of the first and second material layers is a semiconductor material or an electrically insulating material.
 3. The method of claim 2, wherein the first material layer and the second material layer are comprised of a same material.
 4. The method of claim 2, wherein the material of the first material layer is different from that of the second material layer.
 5. The method of claim 2, wherein the semiconductor material is selected from the group consisting of an IV-IV semiconductor, an III-V semiconductor, and an II-VI semiconductor, wherein the III-V semiconductor material is selected from the group consisting of an AlGaInP-based material, an AlGaInN-based material, and an AlGaAs-based material.
 6. The method of claim 2, wherein a frequency of the high-frequency radiofrequency electromagnetic wave is in a range from 3 GHz to 300 GHz.
 7. The method of claim 2, wherein a material of the high-magnetic-permeability material layer is selected from the group consisting of molybdenum-metal, permalloy, electrical steel, nickel zinc ferrite, manganese zinc ferrite, steel and nickel.
 8. The method of claim 2, wherein the first and second material layers are cooled using a cooling fluid.
 9. The method of claim 8, wherein the cooling fluid is selected from the group consisting of liquid nitrogen, dry ice, low temperature air, and low temperature water.
 10. The method of claim 2, wherein the first and second material layers are cooled using a thermoelectric cooler.
 11. The method of claim 1, wherein the first material layer is sapphire. 